Electron transfer in strong-field three-body fragmentation of ArKr 2 trimers.

We experimentally studied the three-body fragmentation dynamics of a noble gas cluster (ArKr 2 ) upon its multiple ionization by an intense femtosecond laser pulse. The three-dimensional momentum vectors of correlated fragmental ions were measured in coincidence for each fragmentation event. A novel comet-like structure was observed in the Newton diagram of the quadruple-ionization-induced breakup channel of ArKr 2 4+ → Ar + + Kr + + Kr 2+ . The concentrated head part of the structure mainly originates from the direct Coulomb explosion process, while the broader tail part of the structure stems from a three-body fragmentation process involving electron transfer between the distant Kr + and Kr 2+ ion fragments. Due to the field-driven electron transfer, the Coulomb repulsive force of the Kr 2+ and Kr + ions with respect to the Ar + ion undergoes exchange, leading to changes in the ion emission geometry in the Newton plot. An energy sharing among the separating Kr 2+ and Kr + entities was observed. Our study indicates a promising approach for investigating the strong-field-driven intersystem electron transfer dynamics by using the Coulomb explosion imaging of an isosceles triangle van der Waals cluster system.